/**
* Executes the current instruction (ROM at pc). Throws ProgramException if the current
* instruction is illegal or if it causes an illegal effect (read/write from M when A is an
* illegal address or jump when A is an illegal address).
*/
public void executeInstruction() throws ProgramException {
short instruction = rom.getValueAt(PC.get());
boolean pcChanged = false;
if ((instruction & 0x8000) == 0) {
bus.send(rom, PC.get(), A, 0);
} else if ((instruction & 0xe000) == 0xe000) {
computeExp(instruction);
setDestination(instruction);
pcChanged = checkJump(instruction);
} else if (instruction != HackAssemblerTranslator.NOP) {
throw new ProgramException("At line " + PC.get() + ": Illegal instruction");
}
if (!pcChanged) {
short newPC = (short) (PC.get() + 1);
if ((newPC < 0) || (newPC >= Definitions.ROM_SIZE)) {
throw new ProgramException("At line " + PC.get() + ": Can't continue past last line");
}
PC.setValueAt(0, newPC, true);
}
time++;
}
